Catalytic converter

ABSTRACT

A catalytic converter for removing noxious pollutants from an exhaust gas stream having a pair of longitudinally spaced conversion chambers mounted therein between its inlet and outlet. Each of said chambers extends diametrically across the converter and each is provided with a pair of opposed faces having openings formed therein whereby the exhaust gases will pass successively through said chambers during their movement from the inlet to the outlet.

United States Patent 1191 Scheitlin 1111 3,771,969 [451 Nov. 13, 1973 [541 CATALYTIC CONVERTER 3,325,256 6/1967 Calvert 23/288 F 3,434,806 3 1969 D R l... [75] 111mm" Gemge schemm Columbus 3,544,264 12/1970 i; A Arv-n Industries 1% Col mbus, 3,561,928 2 1971 Weber 23 288 F [73] Sslgnee u 3,186,806 6/1965 Stiles 23/288 F 3,656,915 4/1972 Tourtellotte 23/288 F [22] Filed: May 10, 1971 3,701,823 10/1972 Hardison 23/288 F X [211 App! Nokmlflso Primary Examiner-Barry S. Richman Attorney-Trask, Jenkins & l-lanley [52] US. Cl. 23/288 F, 60/299, 60/301 [51] Int. Cl FOln 3/14, BOlj 9/04] 57 A T [58] Fleld of Search A catalytic converter for removing noxious pollutants from an exhaust gas stream having a pair of longitudinally spaced conversion chambers mounted therein [56] References Cited between its inlet and outlet. Each of said chambers ex- UNITED STATES PATENTS tends diametrically across the converter and each is 3,016,108 1/1962 Myddelton 23/288 F UX provided with a pair of opposed faces having openings 3,086,839 4/1963 Bloch 23/288 FX formed therein whereby the exhaust gases will pass 3.0901677 5/1963 scheftlfn et alm 23/288 F successively through said chambers during their move- 3,149,925 9 1964 Scheitlm 23 288 F mm from the inlet to the outlet 3,180,712 4/1965 Hamblin 23/288 F 3,228,746 1/1966 Howke et a1. 23/2 E 6 Claims, 9 Drawing Figures 32 33, 3 I2 I5 ,35 4 3218 '98 1 K v x30 7 7: f a 8 I 2O 2O 24 a g 52 (IO 1 I, 52

0 =1 2 48 .=.-1g-=z 48 2 5 27/42 3 Y 47 72 42 37 31 2 44 4e 44 46 kg i 1 E 3g 40 3a 40 5B 38 3 o g g E g S a t 26 922 L "1 PATENTEDuuv 13 1975 3.771. 969 SHEET 2 OF 4 Fi .5 I it w.

ATTORNEYS SHEET t 0F 4 a M? 2% m i g 1 mf E g: M 1 a m is? M i E :1 z :I a :I E :2! :1 a

wxwww -7 PATENTEU NEW 1 3 I873 INVENTOR GEORGE E. SCHEITLIN ATTORNEYS l CATALYTICICONVERTER BACKGROUND OF THE INVENTION Catalytic converters for removing noxious pollutants from an exhaust gas stream are known in the art, as

shown by my prior US. Pat. No. 3,l4 9,925. These pollutants are generally classified into two basic groups; the oxidizable group noxious hydrocarbons and carbon monoxide; and the reducible group the oxides of nitrogen. Because of the different properties of these pollutants, they are most effectively removed from the exhaust gas stream if said stream is subjected to the action of two different catalysts, each selective for one of said groups and each operating in selective oxidizing or reducing atmospheres. The prior art converters have made no provisions for such selective treatment and removal of these two different groups of pollutants.

This invention overcomes the disadvantages of the prior art structures by providing a catalytic converter having a pair of conversion chambers adapted to hold two different catalysts so that the exhaust gases can pass successively through "said chambers and be subjected to the action of the catalysts therein under two different conditions of reaction.

SUMMARY OF THE INVENTION In accordance with one form of the invention, there is provided a catalytic converter provided with an elongated shell closed at its ends by a'pair of end caps. Inlet and outlet conduits project inwardly through said end caps at the opposite ends of said shell and are supported adjacent their inner ends in a pair of baffle plates which form with said shell and end caps a pair of sound attenuating chambers for reducing the noise level of the exhaust gas stream passing through the converter.

First and second conversion chambers adapted to hold catalytic material are mounted in the shell between the inlet and outlet conduits in longitudinally spaced relationship. The chambers extend obliquely across the shell, and each is provided with a pair of opposed perforate faces so that the exhaust gases will pass successively through the chambers during their movement from the inlet conduit to the outlet conduit.

A tube connected to a source of pressurized air extends across the shell between -the two conversion chambers. Said tube has a plurality of longitudinally spaced openings for injecting the air into the shell. With the exhaust gases flowing through the shell, the injected air will be swept to and through the second chamber to permit said chamber to operate in an oxidizing atmosphere as contrasted to the non-oxidizing or reducing atmosphere of the first chamber.

DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a longitudinal vertical section of a catalytic converter embodying the invention;

FIG. 2 is a horizontal section taken on the line 2-2 of FIG. ,1;

FIG. 3 is an enlargedvertical section taken on the line 3-3 of FIG. 1;

FIG. 4 is an enlarged vertical section taken on the line 3-3 of FIG. 1; I

FIG. 5 is a vertical section similar to FIG. 3, but showing a modified form of the conversion chamber;

FIG. 6 is a longitudinal vertical section of a modified form of the catalytic converter shown in FIG. 1;

FIG. 7 is a horizontal section taken on. the line 7--7 of FIG. 6;

FIG. 8 is a vertical section taken on the line 8-8 of FIG. 6; and

FIG. 9 is a vertical section taken on the line 9-9 of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the embodiment illustrated in FIGS. 14, the converter is housed in an elongated shell construction having inner and outer side walls 10 and 12 disposed in spaced relationship with a layer of thermal insulation 15 interposed therebetween. The sidewalls 10 and 12, for strength and economy of space, are in the form of concentric closed curves, an ellipse as shown. The ends of the shell side walls l0 and l2 abut each other'and are rigidly connected, as by common roll seams 18, to a pair of end caps 20-closing the opposed ends of the shell.

A' pair of baffle plates 22 are mounted within the shell slightly inwardly from the end caps 20. Each of said baffle plates is provided with a shouldered aperture 24 disposed in axial alignment with a shouldered aperture 26 formed in each of the endcaps 20. The aligned openings 24 and 26 support an inlet conduit 28 atone end of the converter, and the aligned openings 24 and 26 at the opposite end of the converter support an outlet conduit 30. As shown in FIG. 2, the inlet and outlet conduits are longitudinally misaligned with respect to each other to distribute the weight load of the converter and prevent it from rotating about its center axis when it is mounted on a vehicle. Each of the baffle plates 22 is provided with a plurality of louvered openings 31. The inlet and outlet conduits 28 and 30 terminate inwardly of the baffle plates 22 whereby the spaces between said baffle plates and their adjacent end'caps 20 form a pair of sound attenuating chambers 32 at the opposite ends of the converter; said chambers being acoustically coupled to the gas stream through the baffle plate openings 31, or any convenient resonator throat-formingmembers."

A pair of conversion chamers 33 and 35 are mounted within the'converter in longitudinally spaced relationship. The conversion chambers are adapted to hold catalytic material for removing the noxious pollutants from the exhaust gas stream as it passes through the converter from the inlet conduit 28 to the outlet conduit 30. With a pair of such chambers being employed, each chamber may contain a catalyst selected for a particular type of pollutant. For example, chamber 33 may contain a catalyst specific for removing the oxides of nitrogen from the exhaust gas stream, and the chamber 35 may contain a catalyst for selectively removing the noxious hydrocarbons and carbon monoxide from said stream. Conveniently, in the illustrated embodiment, the chambers 33 and 35 are identical in their construction and their mounting in the converter, and consequently,- only one such chamber will be described herein. y

In the embodiment shown in FIGS. 1-4, each of the chambers is formed by an elongated top wall 37 and a bottom wall 38 interconnected by a pair of imperforate rectangular side walls 39. Said top and bottom walls 37 and 38 are each provided with longitudinally extending rows of slots or louvered openings 40 to permit the exhaust gas stream to flow through the chamber. The forward end of the chamber is closed by an end plate 42 comprising an iinperforate end wall 44 extending across the chamber and integral with a forwardly directed peripheral flange 45. The opposite end of the chamber is enclosed by an end plate 46 comprising an imperforate end wall 47 integrally connected to a rearwardly projecting peripheral flange 48.

Each of the chambers 33 and 35 extends obliquely across the interior of the shell so that the entire exhaust gas stream must pass successively through them during its passage through the converter. The top and bottom walls 37 and 38 have opposed congruent configurations. The top wall edge adjacent the outlet conduit has an arcuate cross-section corresponding to the curvature of the top portion of the shell wall 10, which arcuate cross-section progressively flattens out toward the edge adjacent the inlet conduit into coplanarity. Conversely, the bottom wall edge adjacent the inlet conduit has an arcuate cross-section and said bottom wall progressively flattens out into coplanarity at its edge adjacent the outlet conduit. Thus, the side and bottom stretches of flange 45 on end plate 42 project outwardly from the end of the chamber and are bent laterally outwardly, into abutting engagement with the shell side wall 10, as at 50, and are rigidly secured threto. In a like manner, the side and top stretches of the flange 48 on end plate 46 project outwardly from the chamber and are bent laterally outwardly into abutting engagement with the shell side wall, as at 52, and are rigidly secured thereto. Thus, the end plates 42 and 46 help mount the chambers within the shell and prevent the passage of gas between said chambers and the shell side walls. As shown in FIGS. 1 and 2, the top stretch of flange 45 and the bottom stretch of flange 48 do not project beyond their respective ends of the chamber and thereby reduce the amount of turbulence and back pressure within the converter.

In order to help support the chambers 33 and 35 within the shell, a plurality of longitudinally extending, wedge-shaped braces 54 are interposed between the chamber bottom wall'33 and the bottom portion of the shell side wall 10. As shown in FIG. 3, each of the braces comprises a pair of V-shaped walls 55 having their apex abutting the bottom chamber wall 38 between an adjacent pair of rows of the louvered openings 40 and terminating at their lower ends in laterally projecting fingers 57 rigidly secured to the shell side wall 10. Because of the tilted mounting of the chambers, the brace walls 55 gradually increase in depth from their ends disposed toward the inlet conduit 28 to their ends disposed toward the outlet conduit 30. Conveniently, pluralities of openings 58 are formed in the brace walls 55 to help distribute the gas flow uniformly out of the chambers. While the embodiments shown in FIGS. lshow the braces disposed along only the bottoms of the chambers 33 and 35, it is to be understood, of course, that identical sets of such braces can be interposed between the converter shell and the tops of said chambers.

As shown in FIG. 3, the metal forming the edges of the chamber side walls 39 and the top and bottom walls 37 and 38 is crimped together to form beads 60 projecting obliquely outwardly from the chambers 33 and 35 along their lengths. Said beads are received in inwardly open grooves 62 formed in the shell side wall 10. The metal forming said grooves is crimped over the beads for further rigidly connecting the chambers to the shell and rigidizing the converter assembly.

Because the side walls 39 of the chambers 33 and 35 shown in FIGS. 1-3 are planar, they are spaced from the adjacent portions of the shell side wall'10 and thus provide insulating air spaces along the sides of the chambers. These air spaces are closed by the end plate flange portions 50 and 52, and may be filled with an in sulating material 64.

The chambers 33 and 35 are adapted to hold a catalytic material which effects conversion of the noxious pollutants in the exhaust gases into non-noxious components. Such catalysts may be in the form of pellets inserted into the chambers prior to assembling the end plates thereon. The small size of the slots or louvered openings 40 in the top and bottom walls 37 and 38 prevents the pellets from falling out of the chambers. Conveniently, to refill the chambers, or to fill them after they have been fully assembled, fill tubes 66 are mounted in the shell side walls 10 and 12 and extend into the adjacent chamber side walls 39, said fill tubes being closable by screw caps 68. Thus to fill the chambers with pelletized catalysts, it is merely necessary to remove the caps 68 and pour the catalysts into the chambers through the fill tubes 66.

The catalysts selective for removing the oxides of nitrogen from the exhaust gases require a non-oxidizing atmosphere for most efficient operation, while those selective for removing the carbon monoxide and hydrocarbon pollutants require an oxidizing atmsophere for their most efficient operation. Accordingly, a tube 72 extends across the converter shell between the chambers 33 and 35. As shown in FIG. 2, one end of said tube is closed at 73 and is connected to the shell side wall 10. The opposite end of said tube projects outwardly through aligned openings 74 in the side walls 10 and 12 at the opposite side of the shell for connection to a source of pressurized air. A plurality of longitudinally spaced openings 75 are formed in the tube for injecting air into the converter between the two conversion chambers. With the natural gas flow from the inlet conduit to the outlet conduit, the injected air will be swept along with the gas flow to and through the chamber 35 so that the catalyst therein will be in an oxidizing atmosphere while the catalyst in chamber 33 remains in a non-oxidizing atmosphere.

Thus, in operation of the embodiment shown in FIGS. 1-4, the exhaust gases enter the converter through the inlet conduit 28 and pass into the chamber 33 through its louvered top wall 37. When a pair of selective catalysts are employed in the two chambers, the chamber 33 is filled with a catalyst selective for the oxides of nitrogen. These pollutants are thus removed from the exhaust gas stream as it passes through the chamber 33. The gases exiting chamber 33 through its bottom wall 38 are mixed with the air from the tube 72 and then enter chamber 35 through its louvered top wall 37. The noxious carbon monoxide and hydrocarbon pollutants areremoved from the gases by the catalyst in chamber 35, and said gases exit chamber 35 through its louvered bottom wall 38 for discharge through the outlet conduit 30. During passage of the gas stream through the converter, its noise level will be attenuated by the attenuating chambers 32.

The embodiment shown in FIG. 5 differs from that shown in FIGS. 14 only in the configuration of the side walls 39' of the conversion chambers. As shown, the louvered top and bottom walls 37' and 38' of the chamber are connected to the side walls 39, each of which has an areuate cross-section which abuts the adjacent portion of the shell side wall in face-to-face relationship. This construction eliminates the air spaces along the sides of the conversion chambers and the insulation 64 therein as shown in FIG. 3, as well as the beads and grooves 60 and 62.

In the embodiment shown in FIGS. 6-9, the converter is housed in an elongated shell having concentric inner and outer side walls 110 and 112 disposed in spaced relationship with a layer of insulation 115 interposed therebetween. The ends of said side walls abut each other and are rigidly connected to each other and to a pair of end caps 120 closing the ends of the shell, as by welding.

A pair of baffle plates 122 are mounted within the shell slightly inwardly from the end caps 120. Shouldered apertures 124 are formed in the baffle plates in axial alignment with shouldered apertures 126 in the end caps 120, and an inlet conduit 128 is supportedin one set of said apertures at one end of the converter and an outlet conduit 130 is supported in the other set of said apertures at the opposite end of the converter. As shown, the conduits 128 and 130 terminate inwardly of the baffle plates 122, and each of said plates has a plurality of louvered openings 131 therein so that the spaces between said plates and the end caps form a pair of sound attenuating chambers 132 acoustically coupled to the gas stream through the plate openings 131, or any other convenient resonator throat-forming members.

A pair of conversion chambers 133 and 135 are mounted in the converter in longitudinally spaced relationship with each chamber extending obliquely across the converter shell. The chambers are formed by an elongated top wall 137 and a bottom wall 138 interconnected by a pair of side walls 139 connected to the adjacent portions of the shell side wall 110. As shown in FIG. 6, the walls 137-139 are generally arched such that the opposed ends of the bottom wall 138 abut and are connected to the bott'om portion of the shell side wall 110 with the center portion of saidbot tom wall having a transition section 140 interposed between the chambers 133 and 135 andspacedwe ll'above the bottom portion of said shell side wall. Conversely, the ends of the top wall 137 are spaced from the bottom portion of the shell side wall 110, but the transition section 141 of said top wall interposed between the two chambers abuts and is connected to the adjacent top portion of said shell side wall.

The remote ends of the chambers 133 and 135 are closed by imperforate end plates 142 and 146 connected to the chamber top, bottom and side walls 137-139. The adjacent ends of said chambers are closed by a second pair of end plates 147 and 148 connected to the chamber walls 137-139 at the remote ends of the transition sections 140 and; 141. Conveniently, a plurality of longitudinally spaced, apertured braces 149 are mounted within and extend across each of the chambers 133 and 135. l

In order to permit gas flow through the chambers, the top and bottom walls 137 and 138 are provided with pluralities of slots or louvered openings 150. As shown, the openings 150 are formed only within the extent of the chambers and are not provided with the extent of 1* lustrated herein have been described as employing two different catalysts in the two conversion chambers, it is the transition sections 140 and 141. Thus, all of the gas entering the converter through the inlet 128 passes downwardly through the top wall 137 of chamber 133 and then exits said chamber throughthe bottom wall 138. It then moves upwardly through the bottom wall 138 of chamber and exits saidichamber through the top wall 137 for discharge through the outlet 130. As with the embodiment shown in FIGS. 1-4, the noise level of the gases passing through the converter will be attenuated by the sound attenuating chambers 132.

As shown in FIG. 6, the transition sections and 141, together with the end plates 147 and 148, form a plenum chamber 152 interposed between the chambers 133 and 135. The chamber 152 has a plurality of openings 153 formed in the transition section 140, and a tube 154 adapted to be connected to a source of pressurized air is mounted in the shell side walls 110 and 112 in open communication with said plenum chamber. Thus, the air supplied to the chamber 152 by the tube 154 is discharged through the openings 153 between the outlet of chamber 133 and the inlet of chamber 135. As with the other embodiment, the gas flow through the converter will thus carry the injected air with it so that the chamber 135 can achieve conversion under an oxidizing atmosphere while the chamber 133 can achieve conversion in a reducing atmosphere.

The chambers 133 and 135 may hold the same types of catalysts as the chambers 33 and 35 shown in FIGS. 1-4. Thus, to fill said chambers with pelletized catalysts after assembly, a fill tube 155 is mounted in the shell side walls 110 and 112 and extends into the adjacent chamber side wall within the extent of each of the chambers 133 and 135. Each of the till tubes 15 is closable by a screw cap 156.

The converter is shown in FIGS. 6-9 as having an outer shell and chambers with concentric generally rectangular cross-sections, but it is to be understood, of course, that said shell and chambers can, if it is desired, have any desired cross-sections, such as, for example, the eliptical cross-sections of the embodiment shown in FIGS. 1-5.

While the converter embodiments described and ilto be understood, of'course, that a single catalyst may beemployed if desired. Further, the air tubes 72 and 152 can be connected to suitable valves to prevent the flow of air therethrough if a non-oxidizing atmosphere is desired.

I claim:

' 1. In a catalytic converter for removing noxious pollutants from an exhaust gas stream, an elongated shell having side walls, end caps closing the ends of said shell, gas inlet and outlet conduits in open communication with the interior of said shell adjacent its opposed ends, and first and second longitudinally spaced conversion chambers mounted in said shell inwardly from the ends thereof and extending obliquely across said shell, each of said chambers being adapted to hold catalytic material for removing noxious pollutants from exhaust gases and having top and bottom perforate walls interconnected by a pair of imperforate side walls and a pair of imperforate end plates, said top wall on said first chamber being in open communication with said inlet conduit and said bottom wall on said first chamber being in open communication with the top wall on said second chamber, saidsecond chamber bottom wall being in open communication with said outlet conduit, said end plates projecting longitudinally out.- wardly from the ends of said chambers and being connected to said shell with the portions of said end plates projecting longitudinally outwardly from saidchambers toward the inlet conduit having their top walls removed therefrom and the portions of the end plates projecting longitudinally outwardly from the chambers toward the outlet conduit having their bottom walls removed therefrom.

2. In a catalytic converter for removing noxious pollutants from an exhaust gas stream, an elongated shell having side walls, end caps closing the ends of said shell, gas inlet and outlet conduits in open communication with the interior of said shell adjacent its opposed ends, first and second longitudinally spaced conversion chambers mounted in said shell and adapted to hold catalytic material for removing the noxious pollutants from exhaust gases, each of said chambers extending obliquely across said shell, said first chamber having a first perforate wall surface in open communication with said inlet conduit and a second perforate wall surface in open communication with a first perforate wall surface on said second chamber, said second chamber having a second perforate wall surface in open communication with said outlet conduit, and a plurality of longitudinally extending, laterally spaced braces extending between the bottom of each of said chambers and the adjacent shell side wall.

3. The invention as set forth in claim 2 in which each of said braces is generally wedge-shaped and comprises a pair of V-shaped wals abutting at their apex the bottom wall of one of said chambers between the openings therein, and fingers projecting outwardly from said V- shaped walls rigidly connected to the shell inner side wall.

4. The invention as set forth in claim 2 in which each of said chambers has its end disposed toward the inlet conduit interconnected to the bottom of the shell and its end disposed toward the outlet conduit interconond pair of end plates.

nected to the top of the shell.

5. In a catalytic converter for removing noxious pollutants from an exhaust gas stream, an elongated shell having side walls, end caps closing the ends of said shell, gas inlet and outlet conduits in open communication with the interior of said shell adjacent its opposed ends, and first and second longitudinally spaced conversion chambers mounted in said shell and adapted to hold catalytic material for removing the noxious pollutants from exhaust gases, said first and second chambers extending obliquely across said shell and comprising a bottom wall connected at its opposed ends to the bottom portion of the shell side walls and having a centrally disposed transition section spaced from said bottom portion, a top wall having a centrally disposed transition section connected to the top portion of said shell side walls and having its opposed ends spaced from said top and bottom portions of said side walls, a pair of side walls interconnecting said top and bottom walls, a first pair of end plates connected to said top, bottom and pair of side walls at the opposed ends thereof, and a second pair of end plates connected to said top, bottom and pair of side walls at the opposed ends of said transition sections, each of said top and bottom walls having pluralities of openings formed therein between its transition section and its opposed ends whereby the top wall of said first chamber will be in open communication with siad inlet conduit and the bottom wall of said first chamber will be in open communication with the bottom wall of said second chamber and the top wall of said second chamber will be in open communication with said outlet conduit.

6. The invention as set forth in claim 5 with the addition that said bottom wall has a plurality of openings formed therein within the extent of its transition section, and a tube adapted to be connected to a source of pressurized air is mounted in the shell side walls in open communication with the space between said sec- 

2. In a catalytic converter for removing noxious pollutants from an exhaust gas stream, an elongated shell having side walls, end caps closing the ends of said shell, gas inlet and outlet conduits in open communication with the interior of said shell adjacent its opposed ends, first and second longitudinally spaced conversion chambers mounted in said shell and adapted to hold catalytic material for removing the noxious pollutants from exhaust gases, each of said chambers extending obliquely across said shell, said first chamber having a first perforate wall surface in open communication with said inlet conduit and a second perforate wall surface in open communication with a first perforate wall surface on said second chamber, said second chamber having a second perforate wall surface in open communication with said outlet conduit, and a plurality of longitudinally extending, laterally spaced braces extending between the bottom of each of said chambers and the adjacent shell side wall.
 3. The invention as set forth in claim 2 in which each of said braces is generally wedge-shaped and comprises a pair of V-shaped wals abutting at their apex the bottom wall of one of said chambers between the openings therein, and fingers projecting outwardly from said V-shaped walls rigidly connected to the shell inner side wall.
 4. The invention as set forth in claim 2 in which each of said chambers has its end disposed toward the inlet conduit interconnected to the bottom of the shell and its end disposed toward the outlet conduit interconnected to the top of the shell.
 5. In a catalytic converter for removing noxious pollutants from an exhaust gas stream, an elongated shell having side walls, end caps closing the ends of said shell, gas inlet and outlet conduits iN open communication with the interior of said shell adjacent its opposed ends, and first and second longitudinally spaced conversion chambers mounted in said shell and adapted to hold catalytic material for removing the noxious pollutants from exhaust gases, said first and second chambers extending obliquely across said shell and comprising a bottom wall connected at its opposed ends to the bottom portion of the shell side walls and having a centrally disposed transition section spaced from said bottom portion, a top wall having a centrally disposed transition section connected to the top portion of said shell side walls and having its opposed ends spaced from said top and bottom portions of said side walls, a pair of side walls interconnecting said top and bottom walls, a first pair of end plates connected to said top, bottom and pair of side walls at the opposed ends thereof, and a second pair of end plates connected to said top, bottom and pair of side walls at the opposed ends of said transition sections, each of said top and bottom walls having pluralities of openings formed therein between its transition section and its opposed ends whereby the top wall of said first chamber will be in open communication with siad inlet conduit and the bottom wall of said first chamber will be in open communication with the bottom wall of said second chamber and the top wall of said second chamber will be in open communication with said outlet conduit.
 6. The invention as set forth in claim 5 with the addition that said bottom wall has a plurality of openings formed therein within the extent of its transition section, and a tube adapted to be connected to a source of pressurized air is mounted in the shell side walls in open communication with the space between said second pair of end plates. 